Hepatotoxicity and Oxidative Stress

Hepatotoxicity is an important concern during drug development. In the preclinical phase, potential hepatotoxicity can be detected using animals. Unfortunately, the mechanisms remain often unclear with this approach. The proposition is to construct cell models which allow conclusions concerning mechanisms and which can be used as routine tools in early drug development. 

The liver is one of the main targets of both pharmaceutical drugs and other chemicals (including alcohol). After oral ingestion, they can reach high concentrations in the liver and toxic metabolites can be produced. Drug-associated liver injury is one of the most important reasons for unsuccessful drug development or withdrawal from the market. A key step in liver injury is the excessive production of reactive oxygen species (ROS). Further characterisation of the key events determining the formation of ROS and the consequences of ROS formation for cells and organisms, in terms of cell function and survival, will increase the understanding of what leads to the adverse outcomes of liver injury and liver fibrosis.

This research area aims at understanding toxicity mechanisms related to perturbations in mitochondrial metabolism and Nrf2-signalling in order to identify potential susceptibility factors for liver toxicity, with liver injury/fibrosis as possible adverse outcomes. The research also attempts to identify and characterise key events mediating the transition from oxidative stress to liver damage.

WP1 - Consequences of mitochondrial ROS production on mitochondrial anti-oxidative defense and mitochondrial adaptation in hepatocytes

Rationale for the project

Organelle-specific detection of ROS production and assessment of consequences on the antioxidative system and of adaptive reactions can give valuable information about exposure to toxicants and about toxicological mechanisms. The mitochondrial antioxidative system, superoxide dismutase 2 and peroxiredoxin/thioredoxin as well as the glutathione peroxidase/glutathione systems are particularly important. Mitochondrial fission and mitophagy as well as mitochondrial proliferation are also possible reactions after exposure to mitochondrial toxicants. However, the precise effects on mitochondrial ROS production, adaptation and antioxidative response is still unknown for many compounds.

Objectives

This project aims at establishing reliable in vitro methods for measuring effect on the mitochondrial antioxidative defense system as well as on mitochondrial fission/fusion and mitophagy in hepatocytes. Transgenic in vivo models will also be used in order to investigate effects of impaired mitochondrial antioxidative defense system. Ultimately this may shed light on the question whether an impaired antioxidative defense system is a susceptibility factor for hepatocellular toxicity.

Partners: Jamal Bouitbir, Luigi Terracciano (University Hospital Basel)

WP2 - Importance of the Nrf2 pathway for the hepatotoxicity of ROS-generating toxicants

Rationale for the project

The Nrf2 pathway is essential for the antioxidative defense system and its activation associates with increased synthesis of several key components of the antioxidative defense system. Increased expression of Nrf2 is also associated with a stimulation of mitochondrial functions. Since the Nrf2 pathway is activated by ROS its activation (nuclear translocation of Nrf2) and the expression level of proteins downstream of Nrf2 activation could constitute potential markers of previous ROS exposure.

Objectives

This project will investigate whether toxicants associated with mitochondrial ROS production also activate Nrf2 pathways and related downstream events. For this purpose, hepatocellular in vitro models are utilised to assess hepatotoxicity, as well as in vivomodels with transgenically modified Nrf2 signalling. This will aid in answering whether impaired activation of the Nrf2 pathway is a risk factor for hepatotoxicity of toxicants associated with mitochondrial ROS production.

Partners: Jamal Bouitbir, Luigi Terracciano (University Hospital Basel)

WP3 - Role of Nrf2 in hepatic fibrosis​

Rationale for the project

Liver fibrosis has been identified as an adverse outcome in published Adverse Outcome Pathways (AOPs), but appropriate in vitro models for the investigation of the underlying mechanisms are still lacking. A 3D- human cell co-culture system for the investigation of liver fibrosis has been developed and characterized (in collaboration with InSphero AG). The complex cellular composition (including three cell types) and the longevity of the cultures allows the in vitro investigation of the responses to human-relevant toxicants. 

Objectives

The project objective of this project is to study the underlying molecular mechanisms involved in fibrosis after exposure to toxicants. This includes investigating the role of cellular pathways (Nrf-2- and other pathways) on stellate cell activation in monoculture and in 3D-co-cultures. Another aim is to identify in vitro-in vivo translational biomarkers (from the lab to the clinic) that could serve as diagnostic or prognostic markers for the onset and treatment of liver fibrosis.

Partners: Chris Goldring (University of Liverpool), Stephan Krähenbühl, Luigi Terracciano (University Hospital Basel), Alex Odermatt (University of Basel), Catherine Pilling, Vincenzo Prestigiacomo (University of Applied Sciences and Arts Northwestern Switzerland)